Polyester fiberfill has become widely used and well accepted as a relatively inexpensive filling material for pillows, quilts, sleeping bags, apparel, furniture cushions, mattresses and similar articles. It has generally been made of polyethylene terephthalate staple (i.e. cut) fibers that have been cut from filaments crimped in a stuffer box-type of crimper. The deniers (or dtex) of the fibers have generally been of the order of 5-6, i.e. a significantly higher denier per filament (dpf) than cotton fibers and polyester textile fibers used in apparel; this is because an important requirement for most filling material has been its resilience. The fibers may be hollow or solid, and may have a regular round or another cross section, and are cut to various lengths according to the requirements of the end-use or the process.
Polyester fiberfill is often "slickened", i.e. coated with silicones and more recently with polyethylene terephthalate/polyether segmented copolymers, to reduce the fiber/fiber friction. A low fiber/fiber friction improves the hand of the finished article made from the fiberfill, producing a slicker and softer hand, and contributes to reducing a tendency of the fiberfill to mat (or clump together) in the article during use.
Polyester fiberfill staple has generally been processed by being opened and then formed into webs which are cross-lapped to form a wadding (also referred to as a batt) which is used to fill the article. The performance of articles that have been filled using this technique has been satisfactory in many end-uses for many years, but could not fully reproduce the aesthetics of natural fillings such as down and down/feather blends. Such natural fillings have a structure that is fundamentally different from carded polyester fiberfill batts; they are composed of small particles with no continuity of the filling material; this allows the particles to move around within the ticking and to adapt the shape of the article to the user's contours or desires. We believe that the ease with which down and feather fillings can move around plays a key role in their recovery from compression after being compacted, by simple shaking and patting. This virtue is referred to as refluffability.
Contrary to down and feather, the carded polyester fiberfill batts have a layered structure, in which the fibers are parallelised, and are loosely inter-connected within each web and between the layers so they cannot be moved around and refluffed in a similar way to down and feather. Polyester fillings have, however, some advantages over natural fillings, particularly in regard to washability and durability. Accordingly, Marcus has developed a fiberfill product composed of small, soft polyester fiber clusters or fiberballs which keep their identity during wear and laundering and enable the user to refluff the article filled with the fiberfill. These clusters combine the good mechanical properties and washability of polyester fiberfill with the refluffability of down or down/feather blends.
Although some particulate products had been produced commercially on modified cards from standard fiberfill, such products were prepared for different end-uses, and did not have the properties required for manufacture of high quality bedding or furniture articles. Steinruck disclosed one such modified card and process for making "nubs" in U.S. Pat. No. 2,923,980.
Marcus made his new fiberballs using fibers with specific characteristics as feed for a new fiberball-making process. U.S. Pat. Nos. 4,618,531 and 4,783,364 disclose preferred fiberball products and a process to produce them from spiral crimp (including omega crimp) feed fibers, which can be rolled under mild conditions due to their potential for spontaneous curling. These products have been commercially successful in the U.S. and Europe, mainly in bedding and furniture cushions. Marcus demonstrated that such helical crimp was important for achieving the desired fiberball structure, i.e. in providing a desired random arrangement of the fibers within each fiberball, and in achieving a desired low cohesion between the surfaces of neighboring balls. Commercial fibers with standard mechanical crimp did not produce fiberballs having the desired fiberball structure which provides good durability, high filling power and low cohesion, which are key requirements for refluffable filling products.
To optimize the filling power (i.e. to increase the bulk) and durability (i.e. to lower the amount of bulk lost during use), and particularly the durability to laundering, we believe that the fibers within the fiberball should be randomly distributed, should have a uniform density throughout the structure, and should be sufficiently entangled to keep the fiberball identity through laundering or during normal wear. To achieve optimum filling power and durability, we believe that it is important that each fiber within the fiberball should have its bulk fully and individually developed, so that it can fully contribute (to the filling power and to the durability). To achieve this structure, on which depends the performance of the fiberballs, Marcus used fibers which tend to spontaneously curl, so that a good, consolidated structure could be produced under very mild forces. In the aforesaid patents, Marcus disclosed a preferred way to achieve this desired fiberball structure and properties by using fibers with helical crimp as feed fibers and an air tumbling process to roll the fibers under mild forces. The resulting products are characterized by a random distribution of the fibers within the fiberball, by being at least 50% round (having a ratio of the largest dimension to the smallest dimension of less than 2:1) and by having a low cohesion which was not shown in prior products. Marcus did not produce acceptable fiberballs under the same conditions using commercial fibers with standard mechanical crimp.
The feed fibers used by Marcus to make his new fiberballs are relatively unusual, unavailable and/or expensive in some markets, in which by far the majority of polyester staple fiber is crimped mechanically, generally by a stuffer box technique. Ever since Marcus disclosed the value of using fiberfill in the form of a fiberball, rather than as parallelised fibers in a carded batt-type structure, it has been desirable to find out why standard mechanically crimped fibers did not make good fiberballs, and to provide a feed fiber other than what Marcus used. Snyder et al in U.S. Pat. No. 5,218,740 disclosed another process and apparatus for making fiber clusters, and succeeded in processing mechanically crimped feed fiber into satisfactory fiber clusters. An important object of present application is to provide such mechanically crimped feed fiber that has the capability of being processed into such clusters, sometimes termed fiberballs. Other objects will be apparent herein.
Removable, refluffable cushions are now typical in modern furniture styling. This has created a new need for refluffable fiberfill, so the cushions can be replumped. Furniture also requires filling products having more support and filling power than bedding or apparel. This may require fibers of higher denier. Such fibers may require different crimping conditions from fibers of the order of 5-6 dtex.
In U.S. Pat. No. 4,794,038 to Marcus, there are disclosed fiberballs from spiral crimp fibers and binder fibers which can be molded into a consolidated fiber block. Again, spiral crimped fibers were used to achieve the desired ball structure. It is desirable to provide mechanically-crimped fibers capable of making such fiberballs.
As will be evident herein, the principles of the invention can also be applied to making clusters from fibers other than polyester fiberfill.